Automatic choke carburetor



July 25, 1967 s x 3,332,671

AUTOMATI C CHOKE CARBURETOR Filed Aug. 17, 1966 70 42 T 7 60 1/32 62 al n 72 66 BY (Julia,

A TTOR/VEYS United States Patent 3,332,671 AUTOMATIC CHOKE CARBURETOR Richard M. Saxby, Detroit, Mich., assignor to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed Aug. 17, 1966, Ser. No. 572,987 8 Claims. (Cl. 26139) This invention relates generally to internal combustion engine carburetors, and more particularly to an automatic choke system therefor.

It is old in the art to employ pressure responsive means to actuate a closed automatic choke to a predetermined partially open or qualifying position, against the force of the usual thermostatic spring, upon starting a cold engine and through the initial warm-up period, in order to prevent an over enrichment of the fuel-air ratio and possible stalling of the engine. Such means may also include a so-called choke modulating system which modifies or partially negates the normal choke plate qualifying angle during extremely cold weather conditions. Under such conditions, the normal qualifying position provides too lean a fuel-air ratio for acceptable operating conditions.

While the above mentioned qualifying and modulating systems have, in the past, been combined into single integral assemblies, such assemblies have generally been attached to the carburetor body as separate external units, proving to be both costly and cumbersome, as well as prone to being bumped and damaged.

Accordingly, a primary object of the invention is to provide a pressure responsive combined qualifying and modulating system formed as an integral part of the carburetor body.

A further object of the invention is to provide such a system which requires fewer easily assembled parts and, hence, is less costly than prior systems, cost being a major factor in the carburetor business.

Another object of the invention is to provide such a system which may, in part, be cast as a portion of the carburetor body.

Still another object of the invention is to provide such a system which meets all the functional requirements of prior systems, while having no separate body which may be bumped and/or damaged or which may interfere with lower configuration air cleaners.

Other objects and advantages of the invention will become more apparent when reference is made to the following specification and the accompanying drawings wherein:

FIGURE 1 is a partial side elevational view of a carburetor embodying the invention;

FIGURE 2 is a plan view taken along the line 2-2 of FIGURE 1 and looking in the direction of the arrows;

FIGURE 3 is a fragmentary cross-sectional view taken along the line of 33 of FIGURE 1 and looking in the direction of the arrows; and

FIGURE 4 is a fragmentary cross-sectional view taken along the line of 44 of FIGURE 1 and looking in the direction of the arrows.

Referring now to the drawings in greater detail, FIG- URES l and 2 illustrate a carburetor mounted on an engine intake manifold 12. The carburetor 10- may c-omprise upper and lower bodies 14 and 16 separated by a gasket 18 and secured to each other in some suitable manner, such as by screws 20.

The upper and lower portions 14 and 16 are formed to provide an induction passage having the usual venturi 30 and unbalanced choke plate 24 pivotally mounted therein and secured, as by screws 26, to an off-center choke shaft 28. A fuel reservoir 32 is usually formed as an integral part of the upper and lower portions 14 and 16.

The usual automatic choke bimetallic thermostat telement, shown schematically at 15, may be formed as a part of the upper portion 14, as illustrated by Herman 3,180,576, or it may be mounted on the exhaust manifold, as illustrated herein at 17 and as shown by Saxby 3,088,320, the above mentioned disclosures being incorporated herein by reference.

The choke shaft 28 is operatively connected to the thermostat element by means of a choke lever 34, which is fixedly attached to the end of the choke shaft 28, and suitable linkage 36, which is pivotally mounted between the choke lever 34 and the bimetallic element.

The combined choke qualifying and modulating system 40 is formed'as an integral part of the lower body 16, one portion 42 of which is cast as a cylindrical or other cavity or chamber into the end of the fuel reservoir 32, as better illustrated in FIGURES 3 and 4. A restricted passage 44 (FIGURE 3) communicates between the intake manifold 12 and the chamber 42. The outer edge of a diaphragm 46 (FIGURE 4) is confined between the outer face of the chamber 42 and a cover 48, the cover being secured as by screws 50 (FIGURE 1) and including a cavity 52 (FIGURE 4) and having an outwardly extending cylindrical opening 54 formed thereon.

The central portion of the diaphragm 46 may be confined between a pair of washers 56 and 58 (FIGURE 4), the washer 56 serving as a retainer for a spring 60 mounted in the chamber 42. A stem 62 is secured to and extends outwardly from the washers 56 and 58 through the cylindrical opening 54. A flanged sleeve 64 is slidably mounted on the stem 62 and a retainer 66 is secured to the outer end of the stem 62. A spring 68 is mounted between the retainer 66 and the flange 70 of the sleeve 64 for a purpose which will-be described later.

The bifurcated end 72 (FIGURE 4) of a lever 74 straddles the stem 62, between a shoulder 76 formed thereon and the flanged end 70 of the sleeve 64, the lever 74 being pivotally mounted at an intermediate point 78 thereof on the cover 48. A link 80 is povotally connected between the other end of the lever 74 and an arcuate slot 82 formed in the choke lever 34.

Operation When the engine is started, the bimetallic thermostat spring 15 will, through the link 36, urge the choke lever 34 in a counterclockwise direction (FIGURE 1), cansing the link 80 to contact the left end of the are 82 and holding the choke plate 24 (FIGURE 2) closed. The operation of the choke qualifying system, which works against the force of the thermostatic spring as explained above, will now be explained.

Vacuum from an appropriate source, such as the intake manifold 12, is communicated via the passage 44, to the pressure chamber 42 causing the diaphragm 46 to move rightwardly in FIGURE 4, compressing the spring 60. This causes the lever 74 which straddles the stem 62 to be pivoted about a point 78 in a counterclockwise direction, thereby pulling the link 80 to the left in FIGURE 1 and rotating the choke lever 34 and shaft 28 in a clockwise direction, resulting in an opening movement of the choke plate 24 to a predetermined position. This position, as explained above, is the qualifying setting of the choke. It may be noted that the arcuate slot 82 formed in the choke lever 34 will permit free rotary movement of the choke lever 34, the shaft 28 and the choke plate 24 from this qualifying position to a wide-open choke position during engine warm-up, as permitted by relaxing of the bimetallic thermostat element 15, through the link 36.

While the above described operation prevents an over enrichment of the fuel-air ratio during the warm-up peri-od, under extremely low ambient temperatures when fuel volatility is low, the engine requires a richer fuelair mixture in order to prevent it from stalling out lean. Therefore, a means is required which will, under these cold Weather conditions, partially negate the normal choke plate qualifying angle and provide an enrichment of the fuel-air mixture until the engine warms up sufficiently.

Such a system is known in the art as the choke modulation system, and it is provided in this invention by means of the slidably mounted sleeve 64 and the spring 68. Due to the extremely low ambient temperature, the thermostatic element transmits a stronger than usual force tending to close the choke plate. This force could still not overcome the efiect of the diaphragm 46, except for the calibrated spring 68 and the sleeve 64 slidably mounted on the stem 62. The stronger cold weather force of the thermostatic element 15 is sufiicient to pull the link 36 to the right in FIGURE 1, thereby rotating the lever 34- in a clockwise direction and moving the sleeve 64 to the left in the figure, compressing the spring 68. That is, the spring 68 is calibrated considering the forces applied by the thermostatic element 15 under various temperature conditions so that it will be compressed only under the extreme cold condition, thus negating or di minishing the normal efiect of the diaphragm. In other words, under the extreme cold conditions, the diaphragm 46 will move to its normal position, but the effect of the linkage on the choke plate angle will be changed due to the sliding sleeve.

The choke plate will have thus been moved to a more nearly closed position, during extreme cold, limited only by the calibrated distance which the sleeve 64 is able to move along the stem 62 until coming into contact with the retainer 66. This distance determines the degree of choke plate modulation which may occur until the engine and the bimetallic spring become sufliciently warmed It will be apparent that the invention represents a novel, compact and integral choke qualifying and modulating system, resulting in lower costs, less possibility of damage and better adaptability for the lower configuration aircleaners on modern automobiles.

While but one embodiment of the invention has been shown and described for purposes of illustration, other modifications may be possible, and no limitations are intended except as recited in the appended claims.

What I claim as my invention is:

1. An internal combustion engine carburetor comprising a body including a fuel reservoir, an induction passage, a choke shaft pivotally mounted therein, a choke plate fixedly secured to said shaft Within said induction passage, a choke lever fixedly secured to said shaft, temperature responsive means variably biasing said lever in one direction, a pair of chambers, a pressure responsive device forming a movable wall between said chambers, a stem fixedly secured to said pressure responsive device, a retainer formed on the end of said stem, a sleeve slidably mounted on said stern, resilient means urging said sleeve in one directoin, linkage means pivotally connected between said choke lever and a point between said sleeve and a shoulder formed on said stem, and conduit means connecting said pessure responsive device to a source of engine-induced vacuum.

2. The carburetor described in claim 1, wherein one of said chambers is formed as a cavity in said body.

3. The carburetor described in claim 1, wherein said pressure reseponsive device is a diaphragm.

'4. The carburetor described in claim 3, wherein the other of said chambers is formed by a cover secured to said body in a manner to secure said diaphragm in place.

5. The carburetor described in claim 1, wherein said sleeve includes a flange formed thereon and said resilient means comprises a spring mounted between said flange and said retatiner.

6. The carburetor described in claim 1, wherein said linkage means includes a lever and a link pivotally connected together.

7. The carburetor described in claim 6, wherein said lever is pivotally mounted on said body at a point intermediate the ends thereof.

8. The carburetor described in claim 6, wherein said lever includes bifurcated ends straddling said stem.

References Cited UNITED STATES PATENTS 7/1966 Ball et al. 26l--39 9/1966 Lucas et al 26139 

1. AN INTERNAL COMBUSTION ENGINE CARBURETOR COMPRISING A BODY INCLUDING A FUEL RESERVOIR, AN INDUCTION PASSAGE, A CHOKE SHAFT PIVOTALLY MOUNTED THEREIN, A CHOKE PLATE FIXEDLY SECURED TO SAID SHAFT WITHIN SAID INDUCTION PASSAGE, A CHOKE LEVER FIXEDLY SECURED TO SAID SHAFT, TEMPERATURE RESPONSIVE MEANS VARIABLY BIASING SAID LEVER IN ONE DIRECTION, A PAIR OF CHAMBERS, A PRESSURE RESPONSIVE DEVICE FORMING A MOVABLE WALL BETWEEN SAID CHAMBERS, A STEM FIXEDLY SECURED TO SAID PRESSURE RESPONSIVE DEVICE, A RETAINER FORMED ON THE END OF SAID STEM, A SLEEVE SLIDABLY MOUNTED ON SAID STEM, RESILIENT MEANS URGING SAID SLEEVE IN ONE DIRECTION, LINKAGE MEANS PIVOTALLY CONNECTED BETWEEN SAID CHOKE LEVER AND A POINT BETWEEN SAID SLEEVE AND A SHOULDER FORMED ON SAID STEM, AND CONDUIT MEANS CONNECTING SAID PRESSURE RESPONSIVE DEVICE TO A SOURCE OF ENGINE-INDUCED VACUUM. 